The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The ability to monitor and affect signaling within a neural network and, in particular, within the brain remains an area of research that has broad potential implications in medicine and neural engineering. Within the medical realm, for example, brain stimulation has been shown to relieve and/or prevent symptoms associated with a variety of conditions including, for example, infections, trauma, stroke and other vascular conditions, seizures, tumors, and various neurodegenerative conditions such as Parkinson's disease, Alzheimer's diseases, multiple sclerosis, and others.
The signaling in a biological neural network is based on a highly collective system of electric charges, neurotransmitters and action potentials. The ability to reliably and non-invasively incite and monitor the neuronal charge excitations from outside with the purpose of artificially stimulating the neural network remotely remains an important roadblock to enable advances in the detection, monitoring, and treatment of neurological and related conditions. A neural network can be considered as a complex electrical circuit made of many neurons connected through synapses formed between axons and dendrites. Both types of synapses, known as chemical and electrical synapses, respectively, transfer information between adjacent axons and dendrites directly or indirectly through electric field energy. Consequently, the neural network is sensitive to external electric fields. Moreover, the ability to efficiently control the network at the micro- or nano-scale can enable unprecedented control of important brain functions. Existing technology typically relies on invasive direct-contact-electrode techniques such as Deep Brain Stimulation (DBS), which is one of only a few neurosurgical methods allowed for blinded studies. Existing non-invasive brain stimulation methods include repetitive trans-cranial magnetic stimulation (rTMS) and trans-cranial direct current stimulation (tOCS). rTMS and tDCS represent major advances of the state of the art in non-invasive brain stimulation, but the depth and locality focusing are limited in both methods. In rTMS, high intensity magnetic fields are required to stimulate deep brain regions but high intensity magnetic fields may lead to undesirable side effects.